Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$191.78	10.737%	$212.3714	$212.37	$212.35	$212.40
Purchase #2	$102.88	11.330%	$114.5363	$114.54	$114.55	$114.50
Purchase #3	$88.44	3.634%	$91.6539	$91.65	$91.65	$91.70
Purchase #4	$151.67	11.738%	$169.473	$169.47	$169.45	$169.50
Purchase #5	$113.83	4.149%	$118.5528	$118.55	$118.55	$118.60
Purchase #6	$249.30	12.350%	$280.0886	$280.09	$280.10	$280.10
Purchase #7	$158.94	8.397%	$172.2862	$172.29	$172.30	$172.30
7 purchase totals =	$1,056.84		$1,158.9622	$1,158.96	$1,158.95	$1,159.10